Copper and / or silver doped indium oxide gas sensing material, method for preparing the same and application thereof in high-sensitivity detection of carbon monoxide
By doping indium oxide with copper and silver to achieve local electron redistribution, a highly sensitive gas sensing material that operates at low temperatures was prepared. This solved the problems of high temperature, low sensitivity, and strong cross-sensitivity in In2O3-based sensors when detecting carbon monoxide, and enabled efficient detection of low concentrations of CO.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LIAONING UNIVERSITY
- Filing Date
- 2026-04-21
- Publication Date
- 2026-06-12
AI Technical Summary
Existing In2O3-based gas sensors suffer from high operating temperatures, strong cross-sensitivity, and low sensitivity when detecting carbon monoxide, making it difficult to meet the high-sensitivity detection requirements for low-concentration carbon monoxide in mines.
A one-step solvothermal method was used to dope indium oxide with copper and silver. By taking advantage of the differences in ionic radius and electronegativity between Cu and Ag, local electron redistribution was formed, which increased the number of oxygen vacancies and the surface activity of the material, thus preparing Cux-In2O3, Agy-In2O3, and Cu0.1Agy-In2O3 gas sensing materials.
It achieves highly sensitive detection of carbon monoxide, reduces the operating temperature, and improves selectivity and stability. It is suitable for on-site detection of low concentrations of CO and has good application prospects.
Smart Images
Figure CN122193318A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of materials, specifically to copper and / or silver-doped indium oxide gas sensing materials, their preparation methods, and their application in highly sensitive carbon monoxide detection. Background Technology
[0002] The gas mixture generated during coal mine production is mainly composed of the explosive gas methane (CH4), accounting for 83%-89%, and also contains trace amounts of the asphyxiating gas carbon monoxide (CO). According to coal mine accident data released by the National Mine Safety Administration over the years, from 2000 to 2020, there were a total of 462 major and above accidents caused or induced by coal mine gases, including fires, explosions, and asphyxiation. Gas-induced disasters are a significant threat to coal mine safety. The hazardous gas initially produced by spontaneous combustion of coal (CSC) during coal mining is primarily carbon monoxide (CO), and its presence exacerbates the risk of CH4 explosions. Therefore, detecting carbon monoxide (CO), as an important indicator gas, is of great significance for preventing coal mine disasters and controlling spontaneous combustion of coal.
[0003] Currently, various CO sensing technologies have been developed for detecting carbon monoxide, including optical methods, colorimetric methods, surface acoustic wave methods, electrochemical methods, and chemielectric methods. Among these, metal-oxide-semiconductor (MOS) chemielectric gas sensors are considered ideal sensing materials for detecting various toxic and harmful gases due to their advantages such as excellent response, good stability, low cost, and ease of integration. Among many metal oxides, In₂O₃, as a typical n-type semiconductor, derives its conductivity from electrons provided by donor defects such as oxygen vacancies. It possesses a direct bandgap (E0) at 300 K. g = 3.6 eV) and indirect band gap (E g =2.5 eV), thus exhibiting excellent electrical and optical properties. However, In2O3-based gas sensors suffer from drawbacks such as high operating temperature and cross-sensitivity. To meet the needs of low-concentration carbon monoxide detection in mines, it is necessary to prepare a sensing material for carbon monoxide gas detection that is highly sensitive, highly stable, and has good selectivity.
[0004] Copper- and silver bimetallic doped indium oxide gas sensing materials have irregular surfaces and numerous defects in their structure. The similar ionic radii of Cu (0.72 Å) and In (0.81 Å) allow Cu to easily enter the indium oxide lattice and replace the In metal sites in the In₂O₃ lattice without forming a second phase. Simultaneously, due to the similar ionic radii of Cu (χ²⁻), Cu can readily enter the indium oxide lattice and replace the In metal sites, thus avoiding the formation of a second phase. Cu =1.9) relative to In (χ InThe high electronegativity of Cu (1.7 Å) promotes the redistribution of local electrons between bimetallic sites, improving the adsorption capacity of gas sensing materials for CO. Furthermore, the charge compensation effect caused by Cu anisovalent doping introduces more oxygen vacancies into In₂O₃ as active sites, regulating its electronic structure and catalytic performance. Silver (~1.26 Å), compared to copper (0.72 Å), has a larger ionic radius and cannot directly enter the In₂O₃ lattice, existing mainly as nanoparticles. Due to its unique d-band structure, silver can promote oxygen activation. The introduction of silver solves the high operating temperature drawback of traditional metal oxide semiconductor chemielectric gas sensing materials, lowering the operating temperature for CO response and improving CO selectivity. Bimetallic doped indium oxide gas sensing materials address the low sensitivity problem caused by the limited number of active sites in metal oxides and reduce the energy consumption of gas sensors during operation. A novel high-performance gas sensing material, Cu, was prepared by one-step solvothermal doping with copper, silver, or copper-silver bimetals. x -In₂O₃, Ag y -In₂O₃, Cu 0.1 Ag y -In₂O₃. This gas sensing material features a simple synthesis method, high sensitivity, wide linear range, and low operating temperature, making it well-suited for on-site detection of low-concentration CO and showing promising application prospects. Summary of the Invention
[0005] This invention primarily employs a one-step solvothermal method to dope indium oxide with copper, silver, and a copper-silver bimetallic compound. Cu (0.72 Å), due to its similar ionic radius to In (0.81 Å), can easily enter the indium oxide lattice, replacing In sites and avoiding the formation of a second phase. Furthermore, the charge compensation effect caused by heterovalent doping induces a large number of oxygen vacancies in indium oxide, significantly improving its adsorption of polar gases and surface active oxygen content, thereby achieving highly sensitive detection of carbon monoxide. However, single-metal doping is still insufficient to simultaneously improve the low response value, poor selectivity, and high operating temperature of indium oxide. Therefore, doping with a second metal with complementary effects becomes a highly feasible design strategy. Silver, as a widely used doping element, possesses the ability to improve catalytic activity, enhance selectivity, and increase the surface roughness of materials. Compared to Cu, Ag has unique d... 10 Orbital effects and oxygen spillover effects can lower the activation barrier of oxygen and stabilize intermediates. However, the electronegativity (χ²) between multimetallic sites... Cu =1.9, χ Ag =1.93, χ InThe difference in ionic radius (~1.7) and d0.7 induces a locally asymmetric coordination environment and dipole centers, which can promote the redistribution of interfacial charge and efficient electron transfer, thus improving the adsorption strength of CO to some extent. Furthermore, Ag's large ionic radius (~1.26 Å) and d0.7... 10 The orbital electronic configuration makes it easier to generate Ag nanoparticles on the indium oxide surface, modulates the lowest unoccupied orbital (LUMO) of the material, and improves its selectivity for CO. The Cu-Ag dual-doping strategy makes the indium oxide gas sensing material more responsive to a unit concentration of carbon monoxide and lowers the temperature required for the response, thereby improving its selectivity for CO.
[0006] In(NO3)3·4H2O, Cu(NO3)2·3H2O, and AgNO3 were dissolved in DMF in a certain proportion. The solution was transferred to a hydrothermal reactor and reacted at a certain temperature. The product was collected by centrifugation, washed with anhydrous ethanol, and vacuum dried. The dried material was calcined in a muffle furnace to obtain metal-doped indium oxide gas sensing material. Copper and / or silver were uniformly dispersed on the surface of irregular indium oxide nanoparticles, denoted as Cu. x -In₂O₃, Ag y -In₂O₃, Cu 0.1 Ag y -In2O3, where x and y are the molar ratios of copper and silver to indium, with x being 0.087-0.13 and y being 0.005-0.03.
[0007] The preparation method of the above-mentioned copper and / or silver-doped indium oxide gas sensing material includes the following steps:
[0008] 1) Mix In(NO3)3·4H2O, Cu(NO3)2·3H2O and AgNO3 in a certain proportion, add them to DMF, and disperse them evenly by ultrasonication;
[0009] 2) Transfer the well-dispersed solution to a hydrothermal reactor and place it in an oven for solvothermal reaction;
[0010] 3) The precipitate obtained from the reaction is collected by centrifugation, washed three times with anhydrous ethanol, and then dried in a vacuum oven. The dried precipitate is ground evenly and calcined in a muffle furnace. The calcined material is the indium oxide-doped gas sensing material.
[0011] In the above-mentioned method for preparing copper and / or silver-doped indium oxide gas sensing materials, in step 1), the ratio of In(NO3)3·4H2O: Cu(NO3)2·3H2O: AgNO3 is 1.24 g: 0.087-0.13 g: 0.0035-0.021 g; the amount of DMF is 30-70 mL, and the ultrasonic dispersion time is 10-40 min.
[0012] In the above-mentioned method for preparing copper and / or silver-doped indium oxide gas sensing materials, in step 2), the solvothermal reaction temperature in the oven is 120-180 ℃, and the time is 15-25 h.
[0013] In the above-mentioned method for preparing copper and / or silver-doped indium oxide gas sensing materials, in step 3), the centrifuge speed is 6500 rpm and the centrifugation time is 5-10 min; the vacuum oven temperature is 50-80 ℃ and the drying time is 3-8 h; the muffle furnace temperature is 450-650 ℃ and the calcination time is 2-4 h.
[0014] Application of copper and / or silver-doped indium oxide gas sensing materials in rapid detection of carbon monoxide.
[0015] The above application is carried out using the following method: In a carbon monoxide atmosphere, the above-mentioned metal-doped indium oxide gas sensing material is used to detect carbon monoxide with high sensitivity.
[0016] The beneficial effects of this invention are:
[0017] 1) The synthesis of this invention is simple. A one-step solvothermal method is used to mix In(NO3)3·4H2O, Cu(NO3)2·3H2O, and AgNO3 in a specific ratio, dissolve them in DMF, and carry out the solvothermal reaction. After centrifugation, washing, drying, and calcination, a highly sensitive and rapidly responding gas sensing material is obtained, enabling reliable detection of carbon monoxide, suitable for large-scale production and practical applications.
[0018] 2) The gas-sensitive material prepared by this invention can be used for the detection of carbon monoxide in mines. Cu 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 In₂O₃ exhibits response values of 731±25%, 251%, and 1120±90% to 100 ppm CO at its optimal operating temperature. The gas sensing material Cu prepared in this invention... 0.1 -In2O3 has a short response recovery time. Under the conditions of working temperature of 140 ℃ and 100 ppm CO, the response time is only 25 s and the recovery time is 115 s.
[0019] 3) Cu obtained by this invention 0.1 The In₂O₃ material exhibits excellent reproducibility in its response to CO, with an RSD of 1.08% after 15 repeated measurements. Simultaneously, the material demonstrates excellent linearity (R0) for carbon monoxide concentrations of 10–100 ppb. 2 =0.999).
[0020] 4) Ag prepared by this invention0.01 -In₂O₃, Cu 0.1 Ag 0.02 -In₂O₃ materials exhibit excellent selectivity for carbon monoxide, and a selectivity coefficient (R0) for common interfering gases in mines. CO / R Interfering gas All are greater than 7.6.
[0021] 5) Cu obtained by this invention 0.1 Ag 0.02 In₂O₃ materials exhibit extremely high sensitivity to CO, compared to Cu. 0.1 Ag 0.02 The response temperature of In2O3 decreased from 140 °C to 100 °C. Meanwhile, its response value to 100 ppm CO (1120%) was 13.8 times higher than that of In2O3 (81.2%).
[0022] 6) Cu obtained by this invention 0.1 Ag 0.02 -In2O3 material exhibited excellent repeatability for CO, with an RSD of 3.06 for 15 repeated measurements. Attached Figure Description
[0023] Figure 1 Cu 0.1 Ag y Synthetic route of In2O3.
[0024] Figure 2 Cu 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 Scanning electron microscope image and mapping diagram of In2O3.
[0025] Figure 3 Cu 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 High-resolution transmission electron microscopy of In₂O₃.
[0026] Figure 4 For (a)Cu x -In2O3、(b)Ag y -In₂O₃、(c)Cu 0.1 Ag y X-ray diffraction pattern of In2O3.
[0027] Figure 5 Cu x-In₂O₃: (a) In 3d spectrum, (b) Cu 2p spectrum, (c) O 1s spectrum, Ag 0.01 -In₂O₃ (d)In 3d spectrum, (e)Ag 3d spectrum, (f)O 1s spectrum, Cu 0.1 Ag y -In2O3 (g)Cu 2p spectrum, (h)In 3d spectrum, (i)O 1s spectrum.
[0028] Figure 6 For (a)Cu x -In2O3、(b)Ag y -In₂O₃、(c)Cu 0.1 Ag y Fourier transform infrared spectrum of In2O3.
[0029] Figure 7 For (a)Cu x -In2O3、(b)Ag y -In₂O₃、(c)Cu 0.1 Ag y Fluorescence spectrum of In2O3.
[0030] Figure 8 For (a) the operating temperature of Cu x -Influence of In2O3 on response performance (b)Cu 0.1 -In2O3 response recovery time, (c)Cu x Repeatability test of In₂O₃ against 100 ppm CO at operating temperature of 140 °C, (d)Cu x The response of In₂O₃ to 10⁻¹⁰⁰ ppb CO at an operating temperature of 140 °C, (e)Cu 0.1 -Linear fitting of the response value of In2O3 to the gas concentration at an operating temperature of 140 °C, (f)Cu 0.1 Long-term stability test of In2O3.
[0031] Figure 9 For (a) the effect of operating temperature on Ag y -The effect of In2O3 response performance, (b)Ag 0.01 -In2O3 response recovery time, (c)Ag 0.01 Selective testing of In2O3.
[0032] Figure 10 For (a) the operating temperature of Cu 0.1 Ag y -In2O3 response performance effect, (b)Cu 0.1 Agy -In2O3 response recovery time, (c)Cu 0.1 Ag 0.02 The response of In₂O₃ to 10-100 ppm CO at an operating temperature of 100 °C, (d)Cu 0.1 Ag 0.02 The response of In₂O₃ to 100-1000 ppb CO at an operating temperature of 100 °C, (e)Cu 0.1 Ag 0.02 Repeatability test of In2O3 against 100 ppm CO at operating temperature of 100 ℃, (f) In2O3, Cu 0.1 -In₂O₃, Cu 0.1 Ag 0.02 Selectivity comparison chart of -In2O3. Detailed Implementation
[0033] Example 1: Preparation and characterization of copper-doped, silver-doped, and copper-silver bimetallic doped indium oxide gas sensing materials
[0034] (I) Preparation method
[0035] Synthesis routes of copper, silver, and copper-silver bimetallic doped indium oxide gas sensing materials are as follows: Figure 1 As shown:
[0036] 1) Add 1.24 g In(NO3)3·4H2O, 0-0.1294 g Cu(NO3)2·3H2O and / or 0.0035-0.0210 g AgNO3 to 60 mL DMF and sonicate for 30 min to disperse it evenly;
[0037] 2) Transfer the well dispersed solution to a hydrothermal reactor and place it in an oven to react at 150 °C for 20 h.
[0038] 3) Centrifuge the reacted solution to collect the precipitate. Wash the precipitate three times with anhydrous ethanol, then dry it in a vacuum drying oven at 60 °C for 6 h. Grind the precipitate evenly and calcine it in a muffle furnace at 550 °C for 3 h. The calcined material is Cu. x -In₂O₃, Ag y -In₂O₃ and Cu 0.1 Ag y -In₂O₃. Where x and y represent the molar ratios of copper and silver to indium, respectively, with x ranging from 0.087 to 0.13 and y from 0.005 to 0.03. The molar ratio of Cu was determined experimentally. 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02In₂O₃ exhibits the best carbon monoxide sensing performance, therefore Cu is subsequently used. 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 -In2O3 material was characterized.
[0039] (ii) Characterization
[0040] For the prepared Cu 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 -In₂O₃ was subjected to scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared analysis, and fluorescence spectroscopy. Figure 2 Cu prepared in Example 1 of this invention 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 SEM image of -In2O3, by Figure 2 It can be known that Cu 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 -In2O3 all have a rough spherical morphology, and SEM-Mapping proves the successful doping of the metal. Figure 3 Cu obtained in Example 1 of this invention 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 TEM image of In₂O₃ gas sensing material, by Figure 3 It can be seen that the doped indium oxide gas sensing materials are all spherical particles with a diameter of 40-60 nm, with an uneven surface. No Cu or Ag clusters were found at high resolution, proving that Cu and Ag are uniformly distributed in the material. Meanwhile, Cu... 0.1 The presence of obvious lattice distortion in In2O3 under high-resolution transmission electron microscopy proves the successful doping of metallic copper.
[0041] Figure 4 The images show the XRD patterns of the copper-doped, silver-doped, and copper-silver bimetallic doped indium oxide gas sensing materials prepared in Example 1 of this invention. Figure 4As can be seen, by combining the positions of the diffraction peaks with the standard card for indium oxide, it is proven that the incorporation of copper and silver did not change the crystal structure of indium oxide. The absence of characteristic peaks for Cu or Ag in the XRD pattern indicates that copper and silver are dispersed very uniformly in the material. When Ag is doped alone with a molar ratio of Ag:In reaching 0.03:1, no Ag diffraction peaks were observed in the XRD pattern. However, when Cu and Ag are bimetallic doped, and the Ag:In ratio reaches 0.03:1, obvious Ag diffraction peaks were found in the XRD pattern, proving that Cu and Ag compete with each other during the doping process.
[0042] Figure 5 XPS images of copper-doped, silver-doped, and copper-silver bimetallic doped indium oxide gas sensing materials prepared in Example 1 of this invention. Figure 5 (a) is the In 3d spectrum. As the Cu doping concentration increases, the In 3d peak shifts to higher binding energies, proving that electron directional transfer occurs between Cu and In2O3, and Cu gains more free electrons. Figure 5 (b) is Cu x The Cu 2p spectrum of In₂O₃ shows that the Cu 2p peak shifts to lower binding energies with increasing Cu doping concentration, further supporting the conclusion that Cu... x - The redistribution of local electrons between Cu and In sites in In₂O₃. Meanwhile, when the Cu doping concentration increases to 0.1%, two satellite peaks appearing at 941.3 eV and 943.5 eV confirm the presence of aggregated CuO; the intensity of the satellite peaks increases when the Cu doping concentration increases to 0.13%. Figure 5 (c) shows that as the Cu doping concentration increases from 0 to 0.1, the oxygen vacancy content gradually increases, while when the Cu doping concentration reaches 0.13, the oxygen vacancy content decreases. Oxygen vacancies are an active site in metal-oxide-semiconductor systems, and their presence can improve response performance by suppressing carrier recombination and adjusting the band structure. Figure 5 (d) is Ag 0.01 The In 3d spectrum of In2O3 shows that, compared to In2O3, the In 3d peak shifts significantly to a lower binding energy, proving that Ag doping also involves the redistribution of local electrons. Figure 5 (e) is Ag 0.01 The Ag 3d spectrum of In2O3 confirms the successful Ag doping. Figure 5 (f) is Ag 0.01 - The O 1s spectrum of In2O3, compared to In2O3, Ag 0.01 - Oxygen vacancies in In₂O₃ V The content has increased slightly. Compared to Cu 2+ (0.72 Å), Ag + The ionic radius of (1.26 Å) is larger, much larger than that of In.3+ (0.81 Å) It is not easy to replace the In sites in In2O3. Figure 5 (g) is Cu 0.1 Ag x The Cu 2p spectrum of In2O3 shows that the Cu 2p peak position did not shift significantly with increasing Ag doping concentration. Figure 5 (h) is Cu 0.1 Ag x The In 3d spectrum of In2O3 shows that as the Ag doping concentration increases, the In 3d peak shifts towards higher binding energies, indicating that electrons are redistributed among In, Cu, and Ag in the material. Figure 5 (i) is Cu 0.1 Ag x The O 1s spectrum of In₂O₃ shows that Cu 0.1 Ag 0.02 In₂O₃ has the most active oxygen species among bimetallic doped materials (of which O₂... C Represents chemically adsorbed oxygen, O V (Represents oxygen vacancies).
[0043] Figure 6 The images show the FT-IR spectra of the copper-doped, silver-doped, and copper-silver bimetallic doped indium oxide gas sensing materials prepared in Example 1 of this invention. Figure 6 It can be seen that the stretching vibration peak of the In-O bond in pure indium oxide appears at 607 cm⁻¹. -1 At the same time, the In-O bond stretching vibration peaks of copper-doped, silver-doped, and copper-silver bimetallic-doped indium oxide gas sensing materials showed a redshift compared to pure indium oxide, proving that a local electron redistribution occurred after metal doping. Both FT-IR and XPS analyses confirmed this electron redistribution, a phenomenon primarily influenced by electronegativity and d-orbital electron feedback. Furthermore, the overall direction of electron movement aligned with the electronegativity of the metal, meaning electrons transferred from the less electronegative metal to the more electronegative metal.
[0044] Figure 7 These are fluorescence spectra of copper-doped, silver-doped, and copper-silver bimetallic doped indium oxide gas sensing materials. Fluorescence spectroscopy is used to investigate carrier recombination dynamics, where Cu... 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 The fluorescence intensity of -In₂O₃ is significantly weaker compared to pure indium oxide and other proportions, indicating that the electron-hole recombination rate is significantly suppressed. Oxygen vacancies can act as electron traps to suppress carrier recombination, combined with... Figure 7 and Figure 5 (c) Figure 5 (f) Figure 5 (i) Cu with a relatively higher oxygen vacancy content 0.1 -In₂O₃, Ag 0.01 -In₂O₃, Cu 0.1 Ag 0.02 -In2O3 has a weaker fluorescence intensity compared to materials with other proportions.
[0045] Example 2 Cu 0.1 -In₂O₃ carbon monoxide gas sensing performance test
[0046] Method: Accurately transfer 20 mg Cu 0.1 In₂O₃ material and 100 µL of anhydrous ethanol were ground into a uniform slurry in an agate mortar. The slurry was then brushed onto the surface of a ceramic tube using a brush on an 80 ℃ heating stage to form a gas-sensitive coating. After curing the coated ceramic tube at 450 ℃, the components of the gas sensor were soldered together to obtain the finished sensor. The concentration of the analyte gas in the detection chamber was adjusted by regulating the gas flow rates of a 5000 ppm or 10 ppm (equilibrium gas is dry air) carbon monoxide standard gas cylinder and a dry air cylinder (CO: 1-50 mL / min; dry air: 1-1000 mL / min). The gas mixing process, data acquisition, and output were all completed by the Guizhou Research Institute Jinfeng JF02F gas sensor testing system. The gas sensor is a small hexagonal gas sensor, consisting of a hexagonal base, a heating wire, and a ceramic tube. All gas sensors prepared in this invention were aged using a Winsen WS-64B gas sensor aging bench for 72 hours at a voltage of 3.5 V.
[0047] like Figure 8 As shown in (a), Cu x In₂O₃ exhibits the strongest response to 100 ppm CO at 140 °C, thus determining 140 °C as the optimal operating temperature for copper-doped indium oxide materials. 0.1 -In2O3 exhibited a maximum response of 731%. Figure 8 (b) It can be seen that at 140 °C, Cu 0.1 -In₂O₃ has the shortest response and recovery time, with a response time of 25 s and a recovery time of 10⁴ s. Overall, Figure 8 The result of (a) determines Cu 0.1 -In2O3 is the best material for copper-doped indium oxide. Figure 8 (c) is Cu 0.1The repeatability test of In₂O₃ was performed by repeating the test 15 times under the same conditions with 100 ppm CO. Calculations showed that the RSD of the response value obtained from 15 repeated tests was 1.08%, and the response decay was only 3.5%, proving that Cu... 0.1 -In2O3 exhibits excellent stability. Figure 8 (d) Cu is repeated three times 0.1 The time-varying dynamic response of In₂O₃ to 10⁻¹⁰⁰ ppb CO at 140 °C is shown in the figure. Figure 8 (d) It can be seen that the sensor has good repeatability in the detection results in the low concentration range, combined with Figure 8 (e) shows that there is a linear correlation between the sensor response value and the CO concentration (R0). 2 = 0.999), further confirming its reliability in detecting CO in the low concentration range, a key feature for trace gas monitoring applications. (By...) Figure 8 (f) It can be seen that Cu 0.1 -In2O3 exhibits good long-term stability; after 8 weeks of continuous operation, the response value decays by approximately 11%.
[0048] Example 3 Ag 0.01 -In₂O₃ carbon monoxide gas sensing performance test
[0049] The testing method is the same as above.
[0050] Depend on Figure 9 (a) It can be seen that the silver-doped indium oxide material exhibits the largest response value to 100 ppm CO at 140 °C. Therefore, 140 °C is determined to be the optimal operating temperature for the silver-doped indium oxide material, where Ag... 0.01 -In₂O₃ exhibited a maximum response of 251%. Figure 9 (b) It can be seen that Ag 0.01 The response / recovery times for -In₂O₃ are 93 s and 212 s, respectively. From... Figure 9 (c) It can be seen that when the concentration is 100 ppm, based on Ag 0.01 The In₂O₃ sensor showed a significantly higher response to CO than other common hazardous gases found in mines, such as CH₄, C₂H₆, C₃H₈, CO₂, and NH₃. This indicates that Ag… 0.01 The In₂O₃ sensor exhibits an 8.74-fold higher response to CO than NH₃, which has the same polarity, and is significantly more effective than other nonpolar gases. According to frontier orbital theory, this unique selectivity stems from the altered molecular orbital structure of Ag-doped indium oxide, which enhances the interaction between the indium oxide and CO's HOMO orbitals, thereby strengthening the material's adsorption of CO.
[0051] Example 4 Cu0.1 Ag 0.02 -In₂O₃ carbon monoxide gas sensing performance test
[0052] The testing method is the same as above.
[0053] Depend on Figure 10 (a) It can be seen that at 100 °C, Cu 0.1 Ag y In₂O₃ exhibits the strongest response to 100 ppm CO, and its operating temperature is significantly lower than that of Cu. 0.1 -In₂O₃ (140 ℃). Wherein Cu 0.1 Ag 0.02 -In₂O₃ exhibited a maximum response of 1120%, far exceeding that of Cu. 0.1 -In2O3 (731%) and Ag 0.01 -In₂O₃ (251%). From Figure 10 (b) It can be seen that Cu 0.1 Ag 0.02 The response / recovery time of In₂O₃ is 63 s / 10⁵ s. The lower operating temperature inhibits the diffusion, adsorption, and activation of CO and O₂ on the material surface, resulting in a slower response / recovery rate. Figure 10 (c) and Figure 10 (d) It can be seen that Cu 0.1 Ag 0.02 The In₂O₃ sensor is capable of detecting low concentrations of CO (100 ppb-100 ppm) with high sensitivity under optimal operating conditions. Figure 10 (e) It can be seen that Cu 0.1 Ag 0.02 The In2O3 sensor has an RSD of 3.06% after 15 repeated detections of 100 ppm CO, with a response value decay of about 8%, but still retains about 931% of the response after decay. Figure 10 (f) is In2O3, Cu 0.1 -In₂O₃, Cu 0.1 Ag 0.02 The selectivity comparison chart for In₂O₃, with the interfering gases being common harmful gases found in mines (CH₄, C₂H₆, C₃H₈, CO₂, NH₃), shows that Cu doping significantly improves the response sensitivity of In₂O₃ to CO compared to In₂O₃. However, the selectivity for CO with C₂H₆, C₃H₈, and NH₃ is poor. This is mainly because Cu doping introduces oxygen vacancies and Cu metal sites into In₂O₃, greatly promoting its adsorption and catalytic abilities for polar gases (CO, NH₃). Meanwhile, for C₂H₆ and C₃H₈, the response values increase as the bond energy decreases, demonstrating that Cu doping...0.1 The catalytic activity of In₂O₃ is limited. However, after further Ag doping on top of Cu doping, Cu... 0.1 Ag 0.02 -In₂O₃ exhibited excellent selectivity, with the sensor responding to CO 7.67 times more strongly than NH₃. Combined with Cu 0.1 -In₂O₃ and Ag 0.01 The test and characterization results of In₂O₃ show that after fixing the Cu doping amount to 0.1%, Ag doping further increases the resistivity of the material. Simultaneously, due to the synergistic effect of Cu and Ag, the Cu content is further reduced. 0.1 Ag y The operating temperature of In₂O₃ decreases, and a lower operating temperature reduces the material's response to CH₄ and its homologues (C₂H₆, C₃H₈). Meanwhile, Ag doping alters the Cu... 0.1 Ag 0.02 The band structure of In2O3 and the charge distribution among the multi-metal sites further improve its selectivity for CO.
Claims
1. A copper and / or silver-doped indium oxide gas sensing material, characterized in that, A copper and / or silver source was mixed with an indium source and synthesized via a one-step solvothermal method, followed by calcination. Copper and / or silver were uniformly dispersed on the surface of irregular indium oxide nanoparticles, which were named Cu. x -In₂O₃, where x is 0.087-0.13; Ag y -In₂O₃, where y is 0.005-0.03; Cu 0.1 Ag y -In2O3, where y is 0.005-0.
03.
2. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 1, characterized in that, Includes the following steps: 1) Indium nitrate tetrahydrate, copper nitrate trihydrate, and / or silver nitrate are added to N,N-dimethylformamide and ultrasonically dispersed until uniform; 2) Transfer the well-dispersed solution to a hydrothermal reactor and place it in an oven for a solvothermal reaction; 3) Centrifuge the solution after the reaction to collect the precipitate, wash and dry it, grind the precipitate evenly and calcine it in a muffle furnace to obtain the target product.
3. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 2, characterized in that, In step 1), according to the mass ratio, In(NO3)3·4H2O: Cu(NO3)2·3H2O = 1.24 g: 0.0866 - 0.0996 g.
4. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 2, characterized in that, In step 1), according to the mass ratio, In(NO3)3·4H2O: AgNO3 = 1.24 g: 0.0035 - 0.0210 g.
5. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 2, characterized in that, In step 1), according to the mass ratio, In(NO3)3·4H2O: Cu(NO3)2·3H2O: AgNO3 = 1.24 g: 0.0996 g: 0.0035-0.021 g.
6. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 2, characterized in that, In step 2), the solvothermal reaction temperature is 120-180 ℃ and the time is 15-25 h.
7. The method for preparing a copper and / or silver-doped indium oxide gas sensing material according to claim 2, characterized in that, In step 3), the calcination temperature is 450-650 ℃ and the calcination time is 2-4 h.
8. The application of the copper and / or silver-doped indium oxide gas sensing material of claim 1 in the rapid detection of carbon monoxide.
9. The application according to claim 8, characterized in that, The method is as follows: In a carbon monoxide atmosphere, carbon monoxide is detected with high sensitivity using a copper and / or silver-doped indium oxide gas sensing material as described in claim 1.